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Acceptance Filter
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SPRUI07–March 2020
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Controller Area Network (CAN)
Figure 13-44. Local-Acceptance-Mask Register (LAMn)
31 30 29 28 16
LAMI Reserved LAMn[28:16]
R/W-x R/W-x R/W-x
15 0
LAMn[15:0]
R/W-0
LEGEND: R/W = Read/Write; -n = value after reset (x:Undefined)
Table 13-36. Local-Acceptance-Mask Register (LAMn) Field Descriptions
Bit Field Value Description
31 LAMI Local-acceptance-mask identifier extension bit
1 Standard and extended frames can be received. In case of an extended frame, all 29 bits of the
identifier are stored in the mailbox and all 29 bits of the local-acceptance mask register are used for
the filter. In case of a standard frame, only the first eleven bits (bits 28 to 18) of the identifier and
the local-acceptance mask are used.
0 The identifier extension bit stored in the mailbox determines which messages shall be received.
30:29 Reserved Reads are undefined and writes have no effect.
28:0 LAM[28:0] These bits enable the masking of any identifier bit of an incoming message.
1 Accept a 0 or a 1 (don't care) for the corresponding bit of the received identifier.
0 Received identifier bit value must match the corresponding identifier bit of the MSGID register.
You can locally mask any identifier bits of the incoming message. A 1 value means "don't care" or accept
either a 0 or 1 for that bit position. A 0 value means that the incoming bit value must match the
corresponding bit in the message identifier.
If the local-acceptance mask identifier extension bit is set (LAMI = 1 => don't care) standard and extended
frames can be received. An extended frame uses all 29 bits of the identifier stored in the mailbox and all
29 bits of local-acceptance mask register for the filter. For a standard frame only the first eleven bits (bit
28 to 18) of the identifier and the local-acceptance mask are used.
If the local-acceptance mask identifier extension bit is reset (LAMI = 0), the identifier extension bit stored
in the mailbox determines the messages that are received.
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